The field of the invention pertains to automotive gasoline fuel tanks and the prevention of gasoline vapor release from such tanks to the environment. In particular, the invention is directed to recycling back into the liquid gasoline, the lighter fractions of gasoline such as butane which have vaporized into the head space of a gasoline tank.
In recent years the Reed Vapor Pressure of gasoline, which is a measure of gasoline volatility, has generally increased indicating that most gasoline refiners are producing gasoline with a higher percentage of the lighter more volatile fractions. The loss of gasoline vapors to the environment per gallon produced and sold is therefore increasingly important.
The United States Environmental Protection Agency is currently developing additional Federal test producers to establish allowable vapor emission standards during refueling of motor vehicles. Tighter standards may also be applied to vapor emissions during vehicle operation and as a result of ambient temperature changes.
In addition to adding to the photochemical smog loading of the environment, the refueling vapor emissions are of direct concern due to the benzene content, benzene being a known carcinogen. The potential health effect of exposure to gasoline vapors is taking on increased importance as a general health concern.
A number of systems have been proposed to collect the gasoline vapors at the refueling or service station. Some systems suggest vacuuming up the vapors released at the pump, in particular from the area adjacent the nozzle and fill pipe. Other systems attempt to return vapor from the vehicle tank head space to the storage or supply tank at the service station during the refueling. These systems, however, grow less effective as the Reed Vapor Pressure of the gasoline increases. With the increased Reed Vapor Pressure these systems become more costly to install and maintain and are cumbersome. They are not easily adaptable to all vehicle gasoline tanks for adequate effectiveness.
Many service stations cannot economically support the installation of elaborate systems to control vapor emissions. Two pump and store front stations, in particular, would have great difficulty supporting elaborate systems. Since the gasoline vapors have been originally dispensed as liquid from the gasoline pump, return of the vapors to the service station presents a question of ownership and reimbursement for the vapors returned. Gasoline is a valuable commodity and the vapors lost or returned at a busy service station can total several liquid gallons per day and therefore represent substantial economic value during the course of a year.
Applicant's U.S. Pat. Nos. 3,881,894 and 3,581,782 disclose means and methods for recycling gasoline vapors driven from the head space of an automotive fuel tank back into the underground storage tank of a gasoline station. In the eariler patent applicant also disclosed a means to recycle such gasoline vapors back to the delivery tank or carburetor of a truck used for direct supply of gasoline to automobiles. In both of these disclosures the apparatus for recycling the gasoline vapors is sizable and heavy, being directed to fixed installation at a gasoline station or mounted on a heavy truck.
The later issued above patent discloses a device named a sparger and comprising a labyrinth of microscopic passageways immersed in liquid gasoline. The sparger has been found particularly effective in causing gasoline vapors to be reabsorbed by the liquid gasoline. In a manner not completely understood, the microscopic passageways greatly encourage the dissolution of the vapors into the liquid gasoline.
Because of the wide variety of automobile and truck gasoline tank sizes, the variability and lack of control over the manual refilling of gasoline tanks and maintenance problems with devices attached to the filler nozzle of a gasoline pump, a need exists for an on board completely automatic means to collect and recycle the gasoline vapors in the head space of an automobile gasoline tank. Means are also needed to prevent liquid gasoline splash back and vapor from travelling back up the fill pipe of the tank during refueling.